EP 1 628 382 B1 discloses a rotor for a generator, in particular a high power turbo generator. The rotor has grooves which run axially in a rotor body and have inserted conductor bars which are radially supported in the grooves by means of keys. At the ends of the rotor body, the conductor bars are in each case electrically connected to one another in a rotor end winding. The rotor end windings are in each case covered by a rotor end-bell pushed over the end of the rotor body. An electrically insulating covering channel is arranged in the grooves in each case between the uppermost conductor bar and the key. The covering channel is adjoined, outside the rotor body, by end-bell insulation arranged between the rotor end winding and the rotor end-bell. Furthermore, the covering channels are designed with axially stepped ends at the ends of the rotor body such that the end-bell insulation comprises a ring or a plurality of end-bell insulation segments which are designed toward the rotor body in such a manner that said end-bell insulation segments fit onto the axially stepped ends of the covering channels, and that the rotor end-bell is pushed directly over the end-bell insulation. The rotor end-bell is typically comprised of a high-alloy steel, for example the nitrogen-alloyed special steel P900 from Energietechnik Essen with the material number/DIN code: 1.3816, ASTM A 289, class C.
The development of ever larger turbo generators requires a rotor end-bell of particularly high strength, sufficient shaping properties, an option for non-magnetizability, corrosion resistance and a low weight. There has hitherto been the disadvantage that the forging and finishing of rotor end-bells is very time-consuming, and the high-alloy steels used have high material and manufacturing costs. In addition, because of the restricted availability of the special steels used for the rotor end-bells, delivery bottlenecks may occur at times.